At present, cleaning liquids and gases from various impurities, and separating substances into fractions poses a serious problem. The problem is especially acute when cleaning gases and sewage water in the chemical and petroleum refining industires, in cattle-raising farms, public utilities, ferrous and non-ferrous metallurgy.
There are known apparatus for filtering liquid and gaseous media, each such apparatus comprising a housing accommodating a filtering element and communicating with systems for feeding a medium to be filtered, discharging the clean medium, and evacuating filter cake. Depending on the type of the medium being filtered, used is generally made of filtering elements of a range of designs, such as endless belts, mashes, permeable membranes, etc.
For example, there is known a batch-action apparatus (SU, A, 109199) for cleaning fluid media, in which bag-type filtering elements are secured on two plates of which one such plate is capable of movement for periodically shaking filter bags to remove filter cake from their inside surface.
These apparatus are, however, bulky and inefficient, whereas the filter bags have a tendency to foul and therefore fail to carry out their function; another disadvantage being that the mechanism for shaking the filter bags is also prone to premature failure.
There is known an apparatus (SU, A, 117204) for filtering a fluid medium (liquid) the housing of which accommodates a flexible filtering element in the form of a flexible bag-shaped vessel of a filtering material an open end of which is secured to the housing. The bottom of the vessel is connected by a tie rod to a hoisting mechanism serving to turn the vessel inside out to remove filter cake; this vessel being thus capable of movement relative to the point of its attachment.
The apparatus is structurally simple, although inefficient, since during feeding a batch of the liquid to the vessel cake build-up and clogging of the filtering surface hampers the filtration process, and therefore the vessel needs frequent turning inside out to evacuate the filter cake, which is time consuming.